Polymerization of micelle-forming monomers: Mechanistic study and characterization of the systems before and after polymerization

Cationic surfactants bearing a polymerizable styryl headgroup and a variable alkyl chain with 8–16 carbon atoms have been synthesized. Their aqueous solutions have been characterized by the surfactant critical micellar concentration (CMC) and aggregation number using electrical conductivity, spectrofluorimetry and time-resolved fluorescence quenching. The photoinitiated polymerization of these surfactants in the micellar state led to stable and transparent or slightly bluish systems. The kinetics of polymerization were measured by dilatometry and were found to be close to those obtained for styrene emulsion polymerization. A mechanism of polymerization is proposed and discussed in terms of micellar dynamics. The polymerized systems, p(Cn-STY), and the recovered polymers were characterized by means of several complementary techniques. The polymers have high molecular weights (3 × 10⁵-3 × 10⁶), which indicates that the initial micellar structure is not preserved upon polymerization. The structure of the polymerized systems depends on the alkyl chain length of the surfactant. The p(C16-STY) systems exhibit a structure similar to that of a polysoap with intramolecular hydrophobic microdomains whereas the p(C8-STY) systems behave like classical polyelectrolytes.     

Synthesis and Properties of pH-Dependent Gemini Surfactants Containing Multiple Carboxyl Groups

A series of Gemini surfactants N,N″-dialkyl-N,N′,N″-tripropionate diethylenetriamine (referred as DTPDT-n, where n is the length of the hydrocarbon chain, n = 10, 12, 14) were synthesized, which have three carboxylic head-groups and two hydrophobic alkane chains. The products were characterized by means of nuclear magnetic resonance and mass spectrometry. The physicochemical properties of DTPDT-n surfactants with different hydrocarbon chain lengths were studied such as isoelectric point, surface activities, emulsifying properties, and foam properties. It is showed that these compounds exhibit pH-dependent protonation-deprotonation behavior. The isoelectric points of DTPDT-n surfactants are between 3.40 and 10.90. The critical micellar concentration (cmc) of all three surfactants are lower than the corresponding monomeric surfactants (single head group, single-chain), especially DTPDT-14, whose cmc can reach 2.29 × 10⁻⁵ mol/L. With an increase in the length of the alkyl chain, the solubility of the surfactants decreases and the surface tension of the three surfactants at cmc increases. In consideration of pH, all of three surfactants appear better emulsifying capacity and foaming property under weak alkaline conditions. DTPDT-14 has the best performance of emulsifying capacity among the three surfactants. DTPDT-10 has excellent foaming ability and foam stability.     

Nuclear magnetic resonance studies on hydrolysis kinetics and micellar growth in solutions of surface-active betaine esters

A series of surface-active betaine esters of medium- to long-chain alcohols has been synthesized. The hydrophobic parts used were decyl, dodecyl, tetradecyl, and oleyl chains. Ethyl betainate was prepared as a non-surface-active reference compound. The surfactants were characterized by critical micellization concentration (CMC), and base-catalyzed hydrolysis was studied by using ¹H nuclear magnetic resonance (NMR). Micellar catalysis was shown to have a strong influence on the hydrolysis. This means that the hydrolysis rates are concentration dependent. For dodecyl betainate, the effect of the degradation products (dodecanol and betaine) on the micellar shape was investigated by NMR diffusion experiments. The degradation products were shown to induce micellar growth.     

Colloidal flocculation of micellar solutions of anionic surfactants

Micellar solutions of anionic surfactants usually precipitate in the presence of cations, following a mechanism by which initially cations bind themselves to the micellar surface until saturation is achieved. At higher cation concentrations, unbound cations precipitate with surfactant monomers. In a few cases cations, and especially Al³⁺, cause surfactant micelles to flocculate. These flocs have properties as adsorbents of acidic organic compounds, which might be used in water treatment processes. Both α-olefinsulfonates C₁₄−C₁₆, and laurylsulfate micellar solutions are fast flocculation colloidal systems in the presence of Al³⁺.     

Physicochemical Properties and Phase Behavior of Didecyldimethylammonium Chloride/Alkyl Polyglycoside Surfactant Mixtures

Mixed surfactant systems, used in many formulations, have aroused great attention and interest from researchers and industry due to the possibility of synergism. Alkyl polyglycoside (APG) and didecyldimethylammonium chloride (DDAC) mixtures combine the excellent properties of pure surfactants and play an important role in the development of multi‐functional washing products. To study the synergism between APG and DDAC, the physicochemical properties of different mixed systems have been investigated. The critical micelle concentration (CMC) is about 180 mg·L^?1 and the surface tension at the CMC is about 26.0 mN·m^?1 at a mass fraction of 40 % DDAC (ω_DDAC40 %). The values are significantly lower than pure surfactants. The foaming property shows the best performance at ω_DDAC20 %. When the mass fraction of DDAC is 80 %, the mixture exhibits better wetting and emulsifying properties. Synergism was observed in surface tension, foaming and emulsifying properties, while the wetting ability and detergency exhibited no such effects. Phase behavior of the APG/DDAC/water ternary system has also been carried out by polarized optical microscope. The phase diagram is characterized by a micellar phase, a region where lamellar and micellar phases coexist and a lamellar phase.     

Importance of micellar relaxation time on detergent properties

As we enter the new millennium, manufacturers of laundry detergents would like to provide new products for the twenty-first century. With the goal of achieving new and better performance characteristics, design strategies for research and development should be defined. This paper highlights the importance of micellar relaxation kinetics in processes involved in detergency. Earlier Shah and coworkers showed that the stability of sodium dodecyl sulfate (SDS) micelles plays an important role in various technological processes. The slow relaxation time (τ₂) of SDS micelles, as measured by the pressure-jump technique, was in the range of 10⁻⁴ to 10¹ s, depending on the surfactant concentration. A maximal relaxation time and thus a maximal micellar stability was found at 200 mM SDS (5 s), corresponding to the least-foaming, largest bubble size, longest wetting time of textile, largest emulsion droplet size, and the most rapid solubilization of oil. These results are explained in terms of the flux of surfactant monomers from the bulk to the interface, which determines the dynamic surface tension. More stable micelles lead to less monomer flux and hence to a higher dynamic surface tension. The relaxation time for nonionic surfactants (as measured by the stopped-flow technique) was much longer than for ionic surfactants because of the absence of ionic repulsion between the head groups. The τ₂ was related to dynamic surface-tension experiments. Stability of SDS micelles can be greatly enhanced by the addition of long-chain alcohols or cationic surfactants. In summary, relaxation time data of surfactant solutions enable us to predict the performance of a given surfactant solution. Moreover, results suggest that one can design appropriate micelles with specific stability, or τ₂, by controlling surfactant structure, concentration, and physicochemical conditions, as well as by mixing anionic/cationic or ionic/nonionic surfactants for a desired technological application, e.g., detergency.     

Prediction of CO<Subscript>2</Subscript> mass transfer parameters to light oil in presence of surfactants and silica nanoparticles synthesized in cationic reverse micellar system

CO₂ miscible injection method combined with surfactants and silica nanoparticles was studied to investigate the effect of these additives on CO₂ mass transfer parameters to the light oil, including diffusion coefficient, mass transfer coefficient and solubility. Silica nanoparticles with controlled size distribution were synthesized in isooctane/1-hexanol/CTAB/ammonium hydroxide, a highly-stable reverse micellar system with w _o =5. The presence of Si-O-Si and Si-O-H bonds in FTIR spectra of the system revealed that silica nanoparticles are formed by partial hydrolysis of TEOS. Results of DLS indicated that the average size and size distribution of the synthesized nanoparticles were 27.6 nm and 13-76 nm, respectively. Diffusion tests were carried out using CO₂ gas and three liquid systems: isooctane/1-hexanol, isooctane/1-hexanol/CTAB reverse micellar system without nanoparticles, and isooctane/1-hexanol/CTAB reverse micellar system with nanoparticles. Results of modeling and optimization of the gas-liquid systems under nonequilibrium interface condition, using pressure decay data show that the presence of surfactants and nanoparticles leads to decreased gas diffusion coefficient; while increased interface mass transfer resistance due to presence of aqueous droplets and nanoparticles as well as lower solubility of CO₂ in the light oil are the results of applying these additives, which limits their application. The obtained CO₂ diffusion coefficients for isooctane/1-hexanol, reverse micellar system without nanoparticles, and reverse micellar system with nanoparticles are 8.5550×10^?8, 8.2216×10^?8, and 8.1114×10^?8 m²/s, respectively.     

Study of Foaming Properties and Effect of the Isomeric Distribution of Some Anionic Surfactants

Using different reaction conditions of photosulfochlorination of n-dodecane, two samples of anionic surfactants of sulfonate type are obtained. Their micellar behavior has been already reported and the relationship between their isomeric distribution and their chemical structures and micellar behaviors have been more thoroughly explored. In this investigation, we screened the foaming properties (foaming power and foam stability) by a standardized method very similar to the Ross–Miles foaming tests to identify which surfactants are suitable for applications requiring high foaming, or, alternatively, low foaming. The results obtained for the synthesized surfactants are compared to those obtained for an industrial sample of secondary alkanesulfonate (Hostapur 60) and to those of a commercial sample of sodium dodecylsulfate used as reference for anionic surfactants. The foam formation and foam stability of aqueous solutions of the two samples of dodecanesulfonate are compared as a function of their isomeric distribution. These compounds show good foaming power characterized in most cases by metastable or dry foams. The highest foaming power is obtained for the sample rich in primary isomers which also produces foam with a relatively high stability. For the sample rich in secondary isomers we observe under fixed conditions a comparable initial foam height but the foam stability turns out to be low. This property is interesting for applications requiring low foaming properties such as dishwashing liquid for machines. The best results are observed near and above the critical micellar concentrations and at 25 °C for both the samples.

Electrospinning of chitosan-poly(ethylene oxide) blend nanofibers in the presence of micellar surfactant solutions

Nanofibers were fabricated by electrospinning a mixture of cationic chitosan and neutral poly(ethylene oxide) (PEO) at a ratio of 3:1 in aqueous acetic acid. Chitosan ((1 → 4)-2-amino-2-deoxy-β-d-glucan) is a multifunctional biodegradable polycationic biopolymer that has uses in a variety of different industrial applications. Processing conditions were adjusted to a flow rate of 0.02 ml/min, an applied voltage of 20 kV, a capillary tip-to-target distance of 10 cm and a temperature of 25 °C. To further broaden the processing window under which nanofibers are produced, surfactants of different charge were added at concentrations well above their critical micellar concentrations (cmc). The influence of viscosity, conductivity and surface tension on the morphology and physicochemical properties of nanofibers containing surfactants was investigated. Pure chitosan did not form fibers and was instead deposited as beads. Addition of PEO and surfactants induced spinnability and/or yielded larger fibers with diameters ranging from 40 nm to 240 nm. The presence of surfactants resulted in the formation of needle-like, smooth or beaded fibers. Compositional analysis suggested that nanofibers consisted of all solution constituents. Our findings suggest that composite solutions of biopolymers, synthetic polymers, and micellar solutions of surfactants can be successfully electrospun. This may be of significant commercial importance since micelles could serve as carriers of lypophilic components such as pharmaceuticals, nutraceuticals, antimicrobials, flavors or fragrances thereby further enhancing the functionality of nanofibers.     

13C-NMR analysis of polyoxyethylenated surfactants

Summary ¹³C NMR spectroscopy at 75.46 MHz gives interesting information about the micellar aggregates in aqueous solutions of nonionic oxyethylenated surfactants.The carbon atoms of the ethoxy chain exhibit different chemical shifts depending on the length of the ethoxy chain. This behaviour seems to be related to conformational effects, in particular to the so called gauche- effect.     

Synthesis,Physico-Chemical Properties and Enhanced Oil Recovery Flooding Evaluation of Novel Zwitterionic Gemini Surfactants

In this work, a novel series of zwitterionic gemini surfactants with different hydrophobic tails were synthesized and characterized. The physico‐chemical properties of these products (such as surface tension, oil/water interfacial tension, foaming ability, and the wetting ability of paraffin‐coated sandstone) were fully studied. The CMC of the synthesized surfactants ranged from 2.17 × 10^?4 mol L^?1 to 5.36 × 10^?4 mol L^?1 and corresponding surface tension (γ_CMC) ranged from 26.49 mN m^?1 to 29.06 mN m^?1, which showed excellent efficiency among the comparison surfactants. All the products can reduce the interfacial tension to a relatively low level of about 0.1–1.0 mN m^?1. Additionally, results from applying different hydrocarbons suggested that the synergy will be clearer and oil/water interfacial tension will be lower if the oil components are similar to the surfactants. Contact angle and foaming measurements indicated that the surfactants exhibited good wetting and foaming abilities. The results of oil flooding experiments using an authentic sandstone microscopic model showed that C‐12 and CA‐12 could effectively improve the displacement efficiency by 21–29 %.     

Mixed Micelles of Trisiloxane Based Silicone and Hydrocarbon Surfactants Systems in Aqueous Media: Dilute Aqueous Solution Phase Diagrams, Surface Tension Isotherms, Dilute Solution Viscosities, Critical Micelle Concentrations and Application of Regular Solution Theory

Mixtures of trisiloxane type nonionic silicone surfactant (SS) with sodium dodecylsulfate, tetradecyltrimethylammonium bromide or tert-octylphenol ethoxylated with 9.5 ethylene oxide groups were studied in water at 30 °C by dilute aqueous solution phase diagrams, surface tension and dilute solution viscosity methods. The cloud points for the silicone surfactant aqueous solutions increased upon addition of hydrocarbon surfactants indicating the formation of hydrophilic complexes in mixture solutions. The scrutiny of the surface tension isotherms plotted as a function of SS concentration revealed that competitive adsorption effects are the characteristic features in these mixtures depending upon the SS concentration. Otherwise the isotherms exhibited two break points and the difference of concentration between the two break points increased with the increase in SS concentration indicating the cooperative nature of interactions. The micellar mole fractions of individual surfactants were determined by Rublingh's regular solution theory; interaction parameters and activity coefficients were evaluated and interpreted in terms of synergistic type interactions in these mixtures. The surface active parameters in mixture solutions were estimated and their analysis shows that the molecular species in the mixture solutions have a preferential tendency for adsorption at the air/water interface than in association form in the bulk solution. The effect of hydrocarbon surfactants on the intrinsic viscosity of SS micelles was monitored and related to the enhanced hydration in mixed micelles.     

Synthesis and characterization of polymerizable epoxy resin surfactants

Polymerizable epoxy resin (PER) surfactants have been prepared from the reaction of bisphenol A epoxy resin with acrylic acid, followed by the reaction with polyethylene glycol (PEG) with different molecular weights. The reaction procedures were monitored by chemical titrations, infrared spectroscopy, and NMR. The products show typical surface‐active properties as but much higher water solubility than nonpolymerizable nonionic surfactant OP‐10. With the increase of PEG's molecular weight, the HLB value, the water solubility, and the critical micellar concentration (CMC) of the PER surfactants, the cloud point of the PER surfactant solutions, as well as the solubilization capability of the PER surfactants to organic compounds increase under the experimental conditions. The copolymerization under UV radiation indicated that about 75–80 wt % of PER surfactants participated in the copolymerization with epoxy diacrylate (EdA), except for the PER surfactant with the lowest PEG molecular weight of 1 k. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42598.     

Mixed Micellar and Interfacial Interactions of a Triblock Polymer (EO37PO56EO37) with a Series of Monomeric and Dimeric Surfactants

The mixed micellar and interfacial properties of mixtures of triblock polymer (TBP) with a series of monomeric (dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, and cetyltrimethylammonium bromide, and dimeric (dimethylene bis[alkyldimethylammonium bromide], m-2-m, where m = 10, 12, and 14) cationic surfactants were investigated using surface tension and viscosity measurements in aqueous solutions at different temperatures. Various physicochemical properties such as critical micelle concentration, mixed micellar mole fraction, interaction parameter, interfacial, and thermodynamic parameters were evaluated. All the binary mixtures exhibit synergistic interactions which increase with temperature and pass through a minimum with the increase in hydrophobic chain length of the cationic surfactants. The contribution of TBP in mixed micelle formation also increases with the hydrophobic chain length of the surfactants. The interfacial and thermodynamic parameters reveal that the adsorption of the surfactant mixtures at the air–solution interface is more favorable than that of micelle formation and the unfavorable enthalpy changes are overwhelmed by favorable entropy changes. Further, the mixtures of TBP with smaller chain length surfactants show a sharp rise in relative viscosity at higher mole fractions of these surfactants.     

Micellization of a di‐block copolymer in ethylene glycol and its utilization for suspension of carbonaceous nanostructures

Suspensions of carbonaceous nanoparticles (NPs) in ethylene glycol (EG) can be used as colloidal inks for additive manufacturing and nano‐fluids for heat‐transfer applications. While micellar solutions of surfactants are often used for suspension of the NPs in water, micellization of surfactants in EG is suppressed as compared to aqueous solutions and a well‐defined critical micellization concentration (CMC) is often not observed. Unlike the surfactants, a di‐block copolymer comprising a poly(ethylene glycol) monomethylether methacrylate (PEGMA) segment, 2‐(diethylaminoethyl) methacrylate (DEAEMA) and butyl methacrylate (BMA), poly(O950)‐b‐(DEAEMA‐co‐BMA) was found to assemble into spherical micelles in EG. Surface tension measurements show a well‐defined CMC that depends on the volume fraction of EG. Cryogenic transmission electron microscopy and dynamic light scattering show the presence of spherical micelles with a diameter that reduces with the volume fraction of EG. The micellar solutions were further used for suspending carbonaceous NPs of different geometry and characteristic dimensions: C₆₀ fullerenes, multi‐walled carbon nanotubes, and nanodiamonds. The flow behavior of the suspensions exhibits a relatively low viscosity and mostly Newtonian behavior due to strong interaction between the NPs and the micelles. These suspensions may be used as colloidal inks for two‐dimensional and three‐dimensional printing. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46518.     

Environmentally Friendly Nonionic Surfactants Derived from Tannic Acid: Synthesis, Characterization and Surface Activity

In order to discover new and safe surfactants with regard to the environment, new environmentally friendly nonionic surface active agents were synthesized by the reaction of tannic acid (as a natural product presents in several plants) and polyethylene glycol fatty acids containing different numbers of ethylene glycol units. The fatty acids were dodecanoic, hexadecanoic, octadecanoic and oleic acids. The chemical structures of the synthesized surfactants were confirmed using elemental analysis, infrared and ¹H-NMR spectroscopy. The molecular weights of the synthesized surfactants were determined using viscosity measurements and gel permeation chromatography. The surface properties of these surfactants were determined using surface tension measurements. The chemical structure?Csurface activity relationship of these surfactants showed a strong dependence of the surface activity on their chemical structures including the hydrophobic chains and the number of ethylene glycol units incorporated in the molecules. The free energy of micellization of the surfactants in their solutions showed their tendency towards micellization in the bulk of their solutions, while the free energy of adsorption showed their high tendency towards adsorption at the air?Cwater interface.     

Polymerisation by glow discharge electrolysis

A glow discharge passed from a metal anode to the surface of aqueous solutions of acrylamide produces radicals which initiate polymerisation. The yield of polymer together with its relative molecular mass has been examined as a function of monomer concentration and pressure in neutral solutions. The form of the variations can be explained in terms of a simplified reaction scheme. On the basis of the proposed mechanism there are two reaction zones. In the primary reaction zone no polymerisation occurs, the radical concentration being too high. About 0·2% of the radicals escape into the secondary reaction zone to initiate polymerisation, the volume of this zone being about 0·4 cm³.In alkaline solutions the yields and relative molecular masses of the polymers are very low and this is attributed to chain termination by oxygen which rises from the destruction of hydrogen peroxide in alkaline solution.     

Emulsion polymerization initiated by alkylcobalt–tridentate Schiff base complexes in relation to kinetics and mechanism of their decomposition

Summary Former studies of decomposition of the title alkylcobalt(III)–tridentate Schiff base complexes (RCo) in acidic media have been extended to neutral and alkaline aqueous solutions including micellar ones. In combination, results of both the works indicate a common reaction mechanism, with homolysis of the Co–C bond preceded by substitution of extra ligand(s) with water molecules. Both protons and hydroxyl ions catalyze the latter aquation step after the conventional pattern of acid–base catalysis. Effect of surfactants on the reaction rate has been explained by electrostatic and hydrophilic/hydrophobic interactions between the cationic complexes and other components of micelles formed. On these bases, the use of RCo, which had been formerly proved to be advanced pH-dependent initiators of emulsion polymerization in acidic to neutral media, was extended to alkaline ones. Namely, the emulsion polymerization of styrene was shown to proceed at pH 7 to 13 in the presence of surfactants of any type up to high conversions, but did so, ceteris paribus, much slower than in acidic media. Polystyrene with molecular mass as high as 12 × 10⁶ was thus obtained at pH 9–10. The effect of pH on the rate of emulsion polymerization as well as on characteristics of its products was related to the corresponding rates of decomposition of RCo as well as to stability of emulsion systems and polar interactions in the adsorption layer.     

In situ graft copolymerisation: salami morphologies in PMMA/EP blends: part I

Rubber-modified polystyrene (PS) owes its impact resistance to a morphology of salami domains: in the PS matrix, polybutadiene (PB) domains are dispersed that, in turn, are strongly filled with PS subdomains. This unique structure is created in situ as styrene is polymerized in PB/styrene solutions. The salami domains are built up by graft copolymer chains PB-g-PS. It was suggested previously that these domains assume their characteristic architecture because strongly grafted chains stabilize them on the outside while weakly grafted chains provide their internal substructure. This model is extended in this paper that deals with the polymerisation of methylmethacrylate (MMA) in EP/MMA solutions of a poly(ethylene-co-propylene) copolymer (EP). Intermediate and final products were characterized by ¹H NMR spectroscopy, transmission electron microscopy, two-dimensional chromatography and statistical calculations, with a focus on the pivotal stage of phase inversion during the polymerisation where the salami domains are born.     

Effect of Cationic Surfactant Head Groups on Synthesis, Growth and Agglomeration Behavior of ZnS Nanoparticles

Colloidal nanodispersions of ZnS have been prepared using aqueous micellar solution of two cationic surfactants of trimethylammonium/pyridinium series with different head groups i.e., cetyltrimethylammonium chloride (CTAC) and cetyltrimethylpyridinium chloride (CPyC). The role of these surfactants in controlling size, agglomeration behavior and photophysical properties of ZnS nanoparticles has been discussed. UV–visible spectroscopy has been carried out for determination of optical band gap and size of ZnS nanoparticles. Transmission electron microscopy and dynamic light scattering were used to measure sizes and size distribution of ZnS nanoparticles. Powder X-ray analysis (Powder XRD) reveals the cubic structure of nanocrystallite in powdered sample. The photoluminescence emission band exhibits red shift for ZnS nanoparticles in CTAC compared to those in CPyC. The aggregation behavior in two surfactants has been compared using turbidity measurements after redispersing the nanoparticles in water. In situ evolution and growth of ZnS nanoparticles in two different surfactants have been compared through time-dependent absorption behavior and UV irradiation studies. Electrical conductivity measurements reveal that CPyC micelles better stabilize the nanoparticles than that of CTAC.